This is the exact scenario I'm dreading. Foles is going to look amazing in training camp and especially great if he gets into a preseason game against scrubs. Then the media that always buys into the foles fool's gold will start the chorus that maybe Foles is actually good and just had a bad blip ("after getting hit? ... remember he was great against Arizona and Seattle in the beginning, right? ... etc. etc. etc.)... and then maybe the Rams actually start thinking they were right about that contract all along and they need to keep him around instead of trading him...
Why this is bad in my paranoid little mind is because I'm rooting for Goff to beat out Keenum and start from day 1 and not look back or over his shoulder. If Goff is named starter over Foles -- a former Pro Bowler and #1 starter who still has believers -- there will be a constant QB controversy that Foles ("who looked great in preseason!") gives the Rams the best chance to win now.
Keenum by contrast is seen, fair or not, as a career #2, so the clamor would not be as loud when Goff takes his lumps. Then of course there's the Mannion factor, I want him to stick around and not jettisoned in favor of two guys I personally feel have a limited ceiling.
Foles doing great in camp to be traded is great, but if it lasts beyond that I think it brings the potential for trouble. The Rams signified they were all in for the future giving up so much for Goff, they need to move ahead not backwards.